Process to control pest in stored products

ABSTRACT

The underlying invention involves a process to control pests in stored products, and tobacco products in particular, whereby goods that are prone to infestation are intermittently shock-frozen at temperatures below zero, and whereby the minimum duration and minimum temperature of the shock treatment are selected so as to ensure that the stored product pests are killed in all stages of their development. Accordingly, the underlying invention is advantageous in that it enables effective, long-lasting pest control of goods prone to infestation because it kills not only beetles and their larvae, but also the eggs of the any pests, thus preventing the development of the eggs into the larval stage at a later point in time. Also, the invention&#39;s process makes it possible to eliminate the use of highly toxic chemicals which can leave residues in the treated goods and thereby constitute a health hazard to the consumers thereof. Because it is no longer necessary to use highly toxic chemicals the process is also very economical, in that it eliminates time-consuming and cost-intensive safety measures.

[0001] The underlying invention concerns a process to control pests in stored products. The term “stored products” in particular include dry plant products, such as tobacco products, tea, rice, cocoa, spices, medication and dried fruits.

[0002] The above indicated goods tend to be prone to being infested by pests, including, for example, the biscuit or drugstore beetle (Stegobium paniceum) and the cigarette beetle (Lasioderma serricorne). These stored product pests also frequently infest tobacco products, developing both in the fermented tobacco or in the finished product. The larvae eat their way into the products and pupate in the leaf veins. In cigar manufacturing, this poses a problem which gives results in considerable economic damage. Generally speaking, packaging materials offer but little protection against stored product pests, as the larvae themselves force their way through the smallest cracks and infest the packaged goods. In addition to the economic losses incurred when the products become unusable there is also a significant risk of lost customer loyalty following the purchase of pest-infested products.

[0003] All of these reasons encourage endeavors aimed at pest extermination. To achieve this objective the stored products are customarily treated with fumigants. Fumigants are highly toxic materials such as hydrocyanic acid, phosphoric acid, zinc/calcium/aluminum phosphate, methyl bromide, formaldehyde or ethylene oxide. The product prone to infestation is fumigated with these highly toxic gases, which in particular cause the death of the beetles and larvae. The advantage of these fumigation materials is that because of their high capacity for penetration they not only work on the surface of the goods concerned, but kill pests within the goods as well. The considerable disadvantage of this process is that the treated products retain residue from the fumigation materials, which are not merely limited to their surface and therefore cannot be easily washed away. This residue presents a health hazard for the consumers. This is especially the case with regard to tobacco products, because the toxins in question are absorbed into the body through the mucous membranes of the mouth and into the surface of the lungs as a result of inhalation. What is disturbing about the conventional fumigation processes is that it affects not only unprocessed raw materials but also finished processed goods which are ready for use by consumers. In the case of tobacco products such as cigars, both the fermented tobacco as well as the finished cigars are fumigated. Large quantities of highly toxic gases are used in the final fumigation process in order to ensure that the finished product is free of pests and that the consumers will not receive infested goods. However, this means that residue from highly toxic gases remains in the finished product.

[0004] In addition to the risk to the consumers' health, conventional pest control methods include the disadvantage that, besides the beetles themselves, only the already hatched larvae are generally exterminated, while the eggs themselves are frequently not killed by fumigation. The risk is that larvae will hatch in the finished products from the eggs that survived the fumigation process, which in turn will lead to undesirable damages to the goods in the manner described above, as well as the possible loss of customer loyalty.

[0005] Another disadvantage of the conventionally used process is that special safety procedures must be used when handling fumigants, particularly when handling phosphoric acid and hydrocyanic acid to avoid any risk to employees. This is because these materials are not only highly toxic, but can also combine to form explosive mixtures. Accordingly, strict safety procedures must be observed when storing and handling fumigants. These procedures, besides the increased risk to employees and required cautionary handling procedures, also cost more. Pursuant to the Toxic Materials Ordinance and its pertinent technical regulations, fumigants of this type, in view of their toxicity, may only be issued to companies which hold a permit for these materials. Moreover, the use of such materials may only be undertaken by experts and/or persons holding certificates of qualification.

[0006] Moreover, the fumigation process, in and of itself, is quite expensive. Basically, fumigation involves five steps, which—depending on the size of the object to be fumigated—can take from days to months to implement. Moreover, gas concentration measurements must be taken at the time the fumigants are introduced, during the fumigation monitoring process, during subsequent ventilation and at the time the fumigated goods are released. The objects treated with these chemical substances may only be released when concentration values do not exceed a predetermined threshold. As a result, the exact time periods required for the fumigation process cannot always be scheduled, circumstances, that may, in turn, result in supply delays. Moreover, special-purpose storage areas must be made available for the products until the concentration values have dropped below the permitted threshold.

[0007] All in all, conventionally used fumigation processes for pest control for stored products involve vast amounts of time and are extremely expensive; which, in turn, has a negative effect on the productivity of a processing plant. Furthermore, these products present a considerable health hazard for employees and consumers alike. In addition, the damage to the environment which is incurred through the use of highly toxic chemicals—some of which, such as methyl bromide, also damage the ozone layer—presents an enormous disadvantage.

[0008] Another process to control pests in stored products, which, due to the nature of the risks it presents may only be used in certain countries, involves the use of gamma radiation to eliminate pests. In this case, the risks to the health for employees and consumers alike are considerable, because, in addition to the increased exposure to radiation, this process can involve the formation of carcinogenic radicals in the products.

[0009] In view of all the above stated factors, the objective of the underlying invention is to provide a process for pest control in stored products which would improve on the prior art by providing a means of pest control which would eliminate pests in all stages of their development without making use of substances that are hazardous to health.

[0010] The invention achieves this objective by intermittently shock-freezing the goods prone to infestation, at temperatures below zero, selecting the minimum duration and minimum temperature of the shock treatment so as to ensure that any pests in the stored product are killed in all stages of their development.

[0011] Using the invention's process eliminates all of the prior known disadvantages to an amazing degree. Accordingly, the present invention makes it possible to dispense with current conventionally used fumigation or gamma radiation treatment methods for the purpose of pest control. In this way, the disadvantages and risks associated with said methods of treatment can be advantageously eradicated.

[0012] The invention's use of cold is not only harmless to the end consumers but also to the employees involved in the manufacture of the products concerned. The invention's process means no hazardous residues are left in the products from toxic chemicals. This, in turn, means that the consumers can be certain that they are not ingesting any hazardous materials of this type along with the products concerned. Moreover, this treatment renders the handling of such highly toxic chemicals unnecessary—a fact which in itself presents an advantage with regard to safety in the workplace. Since it is now possible to dispense with the expensive and cumbersome safety precautions needed to store and handle products treated with highly toxic chemicals, the new invention contributes to the cost-effectiveness of the process. Furthermore, a considerably smaller number of work steps is required, thus increasing productivity even further. In addition to the advantageous savings with regard to work steps, it should also be taken into consideration that since product treatment involves only a limited period of time, that the products will no longer need to be stored until the concentration values of toxic substances have dropped below the permitted threshold. This means that the continued use of the products can be planned in the preliminary stages, with no uncertainty parameters with regard to pest control. This is not always possible when conventional fumigation processes are used.

[0013] Besides the advantageous cost savings based on the fact that safety precautions are rendered superfluous, and certain storage capacities are no longer required, the invention's process is significantly kinder to the environmental compared to conventional techniques because no chemicals or radiation which constitute a burden on the environment are used. In this context, the possible elimination of the chemicals applying the invention's process is an advantage, not only in light of the generally desirable reduction of the use of chemicals in pest control, but also in terms of the avoiding the burden which these chemicals place on the environment. The elimination of chemicals is also extremely advantageous because it protects consumers against unnecessary health hazards incurred by using toxic chemicals. There are also considerable economic advantages, especially in view of the more and more crucial awareness shown by consumers with regard to substances of this type, and eliminating chemicals which are hazardous to health can provide an advantage in advertising.

[0014] In the invention's process, the minimum duration and the minimum temperature of the shock treatment are selected so as to ensure that the stored product pests are killed in all stages of their development. The term “pests” should be understood to include not only the beetles, but also their larvae which cause damage to the stored products by eating into them. The invention kills, not only the pests—that is, the beetles and the larvae—but also their eggs, whereas, the eggs of pests frequently survive using conventional fumigation processes. Thanks to the fact that the eggs are killed, the invention's process ensures that no larvae will hatch from surviving eggs during the transport and/or storage of the goods, and, as a result, the goods will not be damaged by them. This being the case, the invention's process minimizes the risk of economic damage from pests because the goods are kept free of pests for long periods of time by killing pest eggs. This means that higher quality standards can be guaranteed, for the benefit of dealers and customers alike.

[0015] Cold treatment can also be advantageously adapted to the various types of pests which infest different kinds of stored products, thereby effectively eliminating numerous kinds of pests. The temperatures used can be adjusted to the different degrees of sensitivity of the individual stored product pests. Accordingly, an extremely wide variety of products which are prone to infestation by stored product pests, and which, in conventional processes, are irradiated or fumigated, may be treated by means by the invention so as to ensure effective and environment-friendly protection against stored product pests. Thanks to the fact that the cytosol in the cells of the respective pests freezes at certain temperatures below zero, it is possible to effectively eliminate the stored product pests in all stages of their development, by forming ice crystals in the cells, which leads to death. In this context, it should be noted that this critical temperature is in the range of a few degrees below zero. Nonetheless, in some cases, somewhat higher temperatures—around the freezing point—are sufficient, especially when a stored product pest is particularly sensitive to cold. The lower the selected shock-freezing temperature, the more quickly the pests will be killed in all stages of their development. The invention proposes that goods which are prone to infestation should be shock-frozen at temperatures of at least −10° C. to −40° C., and preferably −25° C. At these temperature ranges, stored product pests in all stages of their development are killed and eliminated within brief periods of time. Moreover, the use of these temperature ranges is also advantageous because, generally speaking, they correspond to the usual temperatures in cold storage warehouses, meaning that conventional facilities may be used to achieve them. Accordingly, in the simplest case, the goods which are prone to infestation may be stored in a cooling chamber at a sufficiently low temperature and left there long enough to ensure that the pests are killed in all stages of their development. This means that the invention's process will be easy to implement and will not be very expensive or interference-prone, making it exceptionally safe and practicable. The fact that the goods must only be shock-frozen for a relatively brief period of time is advantageous with regard to the duration of the process.

[0016] Furthermore, the cold treatment advantageously preserves the moisture content, taste and aroma of the various stored products. Shock-freezing is especially advantageous in cases where the items being treated consist of finished products; but it may also take place, for example, prior to processing. By means of shock-freezing, the finished products are directly cooled and, for example, they can also be transported or stored in this state. Storage in this state, in addition to the fact that it kills pests in all stages of their development, involves the advantage that moisture content—for example, in tobacco products—is kept basically constant, thus preventing the tobacco from drying out. Moreover, transport and/or storage at these temperatures prevents new infestation of the products by pests present in the transport or storage facility.

[0017] Based on another advantageous developed process it has been proposed that the duration and temperature of the shock-freezing process should be adapted so as to ensure their suitability for the type of stored product in question and the pests to be eliminated. This makes it possible to adjust temperature and cooling duration based on the specific type of stored product to be treated, thus avoiding damage to the product in question. This means the invention process is very flexible with regard to both the goods prone to infestation and the stored product pests to be eliminated effectively making the invention's process applicable to an extremely broad range of products.

[0018] Based on another recommendation, shock-freezing should take place over a period of approx. 24 to 72 hours. Stored product pests are effectively killed during this time span, at temperatures ranging between −10° C. and −40° C., which means the process is generally sufficient for the effective elimination of pests. Nevertheless, stored products can also be kept frozen for longer periods of time, depending on the product type stored—for example, throughout the entire period of transport—in order to avoid new infestation of the goods.

[0019] Another advantageous part of invention moreover proposes that goods prone to infestation should be intermittently treated with microwaves, and that the duration of treatment and average strength of the microwaves be adapted to each one another so as to ensure that pests are killed in all stages of their development. Goods prone to infestation may be irradiated with microwaves before and/or after shock-freezing. The use of microwaves to irradiate goods prone to infestation also leads to the effective killing of pests and their eggs. Therefore, this technology can be used as an additional safety measure, in combination with the cold treatment, in order to ensure that stored products are free of pests.

[0020] The use of microwaves in support of pest control by means of cold treatment is also advantageous because it eliminates the use of highly toxic substances or gamma radiation. Accordingly, this is also advantageous as a supporting measure because this treatment also eliminates materials which are hazardous to health and could leave residue in the products.

[0021] Furthermore, the additional use of microwaves is advantageous in that the treatment need only be implemented for a relatively brief period of time based on their advantageous energy-focusing effect. Microwave treatment breaks down proteins in the pest cells, thus killing pests in all stages of their development. Protracted heating stages, which could damage the stored products in question through the application of high temperatures for long periods of time, can be avoided. Using the invention's process, the products may be warmed evenly without the use of contact heat which could scorch the goods—as, for example, when using a hot plate. Moreover, this has the effect of eliminating the disadvantage, particularly in tobacco production, of drying out the product. Other obvious effects of the treatment—such as scorched spots—are prevented, thus contributing to the attractive appearance of the goods.

[0022] Another preferred development is that potentially infested goods are treated with microwaves for only a brief period of time. The preferred duration of microwave application is less than one minute at approximately 200-1200W, with 700W being preferable. In this context, the duration of treatment should also be adjusted to the amount of goods in question. Using microwave treatment for a brief period of time is especially kind to stored products and prevents the quality of the goods from being harmed in any way as the flavor, aroma and appearance of the goods are not affected by the irradiation. In order to ensure the effective irradiation of large-quantity units, the goods can be moved through the effective irradiation area—for example, by means of conveyors.

[0023] For tobacco, especially that used in the manufacture of cigars, microwave irradiation treatment over a time interval of 10-15 seconds at approximately 700W has proven to be sufficient for small-quantity units—for example, a cigar box. This brief duration of treatment, consisting of only a few seconds, leads to the effective killing of the eggs and larvae of cigarette beetles, but has no negative effect on the quality of the tobacco products themselves. Furthermore, the brief duration of treatment is advantageous in that effective, long-lasting pest control can be achieved in only a short time in the course of manufacturing the finished product.

[0024] All in all, the use of microwaves together with shock-freezing offers the advantage, by means of two mutually complementary measures, of finally and effectively killing any stored product pests, thus ensuring the products are free of pests.

[0025] According to another proposal, pest control by shock-freezing may take place either before or during the processing of stored products, or may be applied to the finished products themselves. Moreover, it is also possible, in the case of certain goods or certain pests, to implement microwave treatment as an additional safety-oriented measure to rule out the possibility of pest infestation in the finished product. Accordingly, in the case of tobacco products, it is possible, for example, to use microwaves for irradiation of the fermented tobacco and/or the finished product—such as, for example, a cigar. The treatment of the finished product by means of shock-freezing and/or microwaves is simple to implement and has the advantage of rendering the final fumigation stage which uses large quantities of highly toxic fumigants, unnecessary. Accordingly, the invention's process is well suited for avoiding this final fumigation stage, which means residue from these highly toxic fumigants which can remain in the products, can be avoided. The treatment of the finished products by this invention's process is simple, and existing facilities can be adapted to the process at no great expense, thus allowing the final fumigation stage to be skipped—a fact which presents a significant advantage over conventional processes and is also advantageous for the users of the finished products, which remain chemical-free.

[0026] A more detailed description of the underlying invention is found below in the form of detailed examples. An example is given solely for the purpose of a more precise description and is not to be regarded as limiting. The example in question relates to the use of the invention's process to control cigarette beetles in tobacco during the manufacture of cigars. In the example at hand, the finished cigars undergo pest control treatment.

[0027] In order to ensure that no pests can contaminate and/or damage the goods, upon the conclusion of their manufacture the cigars are treated in order to prevent pest infestation. Specifically, the cigars are shock-frozen for about 72 hours at approximately −25° C. During this interval, beetles, larvae and eggs of the stored product pests in question—in the present example, the cigarette beetle (Lasioderma serricorne)—are effectively killed. The cigars can be transported in this state and no additional storage is required for the cooled cigars. At a later stage, the cigars are slowly thawed. Cigars treated in this manner have an aroma which is in no way compromised by the treatment, and furthermore, they contain no residue of chemicals used for pest control—a fact which is an advantage with regard to the health of the user.

[0028] The invention's process can be used in a wide variety of applications related to pest control. It has proven especially effective with regard to control of the cigarette beetle (Lasioderma serricorne) which can infest a broad range of stored products including tobacco products, spices, medication and dried fruits. Applying the new process on tobacco has been shown to be very effective; and, the process can also be used for other stored products and compares favorably against other stored product tests. Thanks to the low cost and relatively little effort involved in its use in pest control, the invention saves both time and money, eliminating stored product pests in a manner which is both more effective and environment-friendly than conventional methods; this is an advantage for consumers because the products are not altered in any way, and no hazardous chemical residue remains in the products. In addition, the invention's process takes only a short time and is further characterized by the simplicity of its implementation and not being significantly prone to interference. 

1. Process to control pests in stored products, especially in tobacco products, wherby goods which are prone to infestation are intermittently shock-frozen at temperatures below zero, the minimum duration and minimum temperature of the shock treatment are selected so as to ensure that the stored product pests are killed in all stages of their development.
 2. Process according to claim 1, whereby stored products are shock-frozen at temperatures of at least −10° C. to −40° C., preferably −25° C.
 3. Process according to either of claims 1 or 2, whereby the duration and temperature of the shock-freezing process are adapted to each other so as to ensure their suitability for the type of stored product in question.
 4. Process according to one or more of claims 1 to 3, whereby the shock-freezing takes place over a period of up to 72 hours.
 5. Process according to one or more of claims 1 to 4, whereby the shock-freezing takes place at the end of the product manufacturing process.
 6. Process according to one or more of claims 1 to 5, whereby the goods prone to infestation are intermittently treated with microwaves, whereby the duration of treatment and the average strength of the microwaves are adapted to each other so as to ensure that both the pests themselves and their eggs are killed.
 7. Process according to one or more of claims 1 to 5, whereby the goods prone to infestation are irradiated with microwaves before and/or after shock-freezing.
 8. Process according to one or more of claims 1 to 7, whereby goods prone to infestation are treated with microwaves for less than one minute at approximately 200-1200W, preferably at 700W, whereby parameters are adjusted to the quantity of goods prone to infestation to be irradiated.
 9. Process according to one or more of claims 1 to 8, whereby the microwave frequency used is adjusted to the required depth of penetration of the goods by the microwaves, whereby microwaves are used in a range of 2 to 20 GHz, preferably 2 to 5 GHz.
 10. Process according to one or more of claims 1 to 9, whereby the duration of treatment, temperature and average strength of the microwaves are adapted to each other so as to ensure that both the pests themselves and their eggs are killed, but that the stored products themselves are not damaged. 